Back Up PC or Laptop

+1

Buy an external hard disk and back up your contents.

If you want to be back up and running in an emergency, with the latest copies of your files at hand, you'll have to make sure to do those backups very regularly.

In that case, I would recommend a program like SyncBackPro, and set it to copy all your required files every night, at minimum.
 
Remind me never to use your PC...

You generally don't want the kids playing on the PC you do your accounts on, or run your business from, or you work laptop. People in IT might have different projects on different machines with different OS'es. You might have a Media PC connected to the TV, but you might not want someone doing their college projects on it. You don't want someone downloading a facebook game virus on your work machine.